This invention relates to an image encoding apparatus for compression of information of images.
Various image encoding apparatus by means of discrete cosine transform (DCT) have been known in the art. Conventionally, an image encoding apparatus includes a two-dimensional digital DCT circuit and a quantization circuit formed by a digital division operation unit and employs digital processing technology. A series of analog signals from an image sensing element such as a CCD (charged-coupled device) is converted by an ADC (analog-to-digital converter) into a series of digital signals. The digital signal series is temporarily held in an image memory. In the two-dimensional digital DCT circuit a two-dimensional DCT is performed on the digital signal series applied from the image memory in pixel blocks. In order to quantize a result of the two-dimensional DCT performed by the two-dimensional digital DCT circuit, the quantization circuit carries out a division operation of dividing a digital value representing the transform result by a quantization coefficient Q.
However, a disadvantage of the above-described image encoding apparatus is that both the two-dimensional digital DCT circuit and the quantization circuit, formed of a digital division operation unit, are large in circuit scale. This means that there is still room for improvement of the conventional image encoding apparatus, to provide, a compact, low-power, and low-cost image encoding apparatus.